ABSTRACT
Peyer's patch follicle-associated epithelium (FAE) regulates intestinal antigen access to the immune system in part through the action of microfold (M) cells which mediate transcytosis of antigens and microorganisms. Studies on M cells have been limited by the difficulties in isolating purified cells, so we applied TOGA mRNA expression profiling to identify genes associated with the in vitro induction of M cell-like features in Caco-2 cells and tested them against normal Peyer's patch tissue for their expression in FAE. Among the genes identified by this method, laminin beta3, a matrix metalloproteinase and a tetraspan family member, showed enriched expression in FAE of mouse Peyer's patches. Moreover, the C. perfringens enterotoxin receptor (CPE-R) appeared to be expressed more strongly by UEA-1(+) M cells relative to neighboring FAE. Expression of the tetraspan TM4SF3 gene and CPE-R was also confirmed in human Peyer's patch FAE. Our results suggest that while the Caco-2 differentiation model is associated with some functional features of M cells, the genes induced may instead reflect the acquisition of a more general FAE phenotype, sharing only select features with the M cell subset.
Subject(s)
Cell Culture Techniques , Epithelial Cells/physiology , Peyer's Patches/cytology , Peyer's Patches/physiology , Animals , Caco-2 Cells , Cell Culture Techniques/methods , Cell Differentiation/immunology , DNA Primers , Gene Expression Profiling , Humans , Immunohistochemistry , In Situ Hybridization , Reverse Transcriptase Polymerase Chain Reaction , Species SpecificityABSTRACT
Mammalian Peyer's Patches possess specialized epithelium, the follicle associated epithelium (FAE), and specialized cells called M cells which mediate transcytosis of antigens to underlying lymphoid tissue. To identify FAE specific genes, we used TOGA gene expression profiling of microdissected mouse Peyer's Patch tissue. We found expression of laminin beta3 across the FAE, and scattered expression of peptidoglycan recognition protein (PGRP)-S. Using the M cell specific lectin Ulex europaeus agglutinin 1 (UEA-1), PGRP-S expression was nearly exclusively co-localized with UEA-1+ M cells. By contrast, the related gene PGRP-L was expressed among a subset of UEA-1 negative FAE cells. Expression of these proteins in transfected cells demonstrated distinct subcellular localization. PGRP-S showed a vesicular pattern and extracellular secretion, while PGRP-L showed localization to both the cytoplasm and the cell surface. The potential function of these PGRP proteins as pattern recognition receptors and their distinctive cellular distribution suggests a complex coordination among specialized cells of the FAE in triggering mucosal immunity and innate immune responses.
